Pituitary adenoma

Jai Grewal MD (Dr. Grewal of the Long Island Brain Tumor Center at Neurological Surgery, PC, received research funding from Northwest Biotherapeutics and consulting fees from Novocure.)
Harpreet K Grewal MD (Dr. Grewal of JGMDPC in Roslyn, New York, has no relevant financial relationships to disclose; Dr. Grewal's spouse received research funding from Northwest Biotherapeutics and consulting fees from Novocure.)
Edward J Dropcho MD, editor. (Dr. Dropcho of Indiana University Medical Center has no relevant financial relationships to disclose.)
Originally released April 18, 1994; last updated September 1, 2014; expires September 1, 2017

This article includes discussion of pituitary adenoma and prolactinoma. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.

Overview

Pituitary adenomas represent 9% of intracranial neoplasms. Typical presenting manifestations include amenorrhea, infertility, visual field abnormalities, and headache. Diagnosis is often made with brain MRI, visual field testing, and serum hormone assay. Prolactinoma, the most common type of pituitary adenoma, usually responds to therapy with a dopamine agonist such as bromocriptine or cabergoline. Rare refractory cases, large tumors, and pituitary adenomas that secrete other hormones are often treated with transsphenoidal surgical resection. Stereotactic radiosurgery is emerging as a second-line option. In this article, the authors discuss surgical options and the role of stereotactic radiosurgery in treating pituitary adenomas.

Key points

 

• Pituitary adenomas represent 9% of intracranial neoplasms.

 

• Typical presenting manifestations include amenorrhea, infertility, visual field abnormalities, and headache.

 

• Diagnosis is often made with brain MRI, visual field testing, and serum hormone assay.

 

• Prolactinoma, the most common type of pituitary adenoma, usually responds to therapy with a dopamine agonist such as bromocriptine or cabergoline.

 

• Rare refractory cases, large tumors, and pituitary adenomas that secrete other hormones are treated with transsphenoidal surgical resection first-line.

 

• Stereotactic radiosurgery has largely replaced external-beam radiotherapy as a second-line treatment option.

Historical note and terminology

The classification of pituitary adenomas has changed considerably over time. The first attempts at classification relied on hematoxylin and eosin staining of resected tissue. Adenomas were categorized as acidophilic, basophilic, or chromophobic. This scheme, however, failed to account for clinical manifestations or hormone secretion. Modern histologic evaluation utilizes immunoperoxidase staining techniques to identify the hormones within adenoma cells. This form of analysis proves that acidophil and chromophobe cells may produce the same hormones (prolactin, growth hormone, or thyroid-stimulating hormone), whereas basophil cells produce any of the other anterior pituitary hormones (adrenocorticotropic hormone, beta-lipotropin, luteinizing hormone, or follicle-stimulating hormone).

Malignancy has occasionally been used to classify pituitary tumor types. However, pituitary adenocarcinoma is extremely uncommon, and this distinction has not been clinically useful in understanding the large number of benign pituitary tumors. Malignancy can only be diagnosed unequivocally on the basis of metastases, as rapidly growing adenomas may demonstrate variation in cell and nuclear size and shape, similar to changes seen in a carcinoma; therefore, histology is not a reliable indicator of malignancy for this tumor (Cotran et al 1994).

Tumor size is frequently used to categorize pituitary tumors as microadenomas (less than 10 mm in diameter) and macroadenomas (10 mm or greater in diameter). This distinction is easily made in the era of high-resolution neuroimaging. With the advent of radioimmunoassay, a sensitive technique that allows for measurement of pituitary hormones in the serum, endocrine function is now often used to classify pituitary tumors. Pituitary adenomas may secrete 1 or several hormones, and approximately one-third do not secrete any hormone at all. The latter are sometimes referred to as “null cell” or nonfunctional adenomas. Of the hormone-secreting adenomas, 60% to 70% secrete prolactin, 10% to 15% secrete growth hormone, a small number secrete adrenocorticotropic hormone, and rare tumors secrete gonadotropins or thyroid-stimulating hormone (Victor and Ropper 2001).

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